Resinous compositions for wire coatings and the like



A. O. BLADES April 2, 1946.

RESINOUS COMPOSITIONS FOR WIRE COATINGS AND THE LIKE Original Filed Aug.2, 1940 CONDUCTOR Fi l. 4

R O T C U D N O C (\INSULATION INVENTOR ANSLEY O. BLADES 3;;

a ATTORNEY meme A r. 2,61946 UNITED STATES PATENT, osmos- RESINOUSCOMPOSITIONS FOR WIRE COATINGS THE LIKE Original application August 2,1946, Serial No.

Divided and this application 1942, Serial No. 451,312

1 Claim. (01. 260-27) This invention relates to improvements inincables, and more particularly to synthetic resin compositionstherefor, and to plasticizers used to impart to such compositionscertain qualities desirable for these'coverings. Some resins, as forexample, the polyvinyl chloride resins, are less tough, more brittle,and less cohesive, and therefore less suitable, for such coverings thancertain copolymer resins such, for example, as the copolymer produced bythe conjoint polymerization of vinyl chloride and vinyl acetate.However, some of these copolymers, including that of vinylchloride andvinyl acetate, require plasticizing before they can be used efiectivelyfor this purpose.

This application is a division of my copending application for patentfor Plasticizers for resinous compositions used forwire coatings, filedAugust 2, 1940, Serial No. 350,132; and issued on Sept. 14, 1943, asPatent No. 2,329,583.

An illustrative embodiment of the invention selected merelyiordescriptive'purposes is shown in the accompanying drawing, in which:

Figure 1 is a side elevation of an insulated conductor, the insulationcoating being cut back so as to disclose the conductor; and

Figure 2 is a cross section on the line 2-2 of Figure 1.

The legends appearing on the drawing are for illustrative purposes onlyand are not by way I of limitation.

In respect of plasticizers to be used in electrical insulatingcompositions, they must be compatible with the resin with which they areto be blended; and it is very important that, when blended with theresin, they should produce a compound that is easy to handle duringplasticized copolymer compositions have a power factor of 5% or over anda dielectric constant of 5 or over.

I have discovered that such a plasticizer may be produced by combininghydrogenated methyl sulating and protective coverings for wires and July17,

abietate either with an ester, such as dioctyl phthalate, which has twohydrocarbon chains of at least eight carbon atoms each, or with an esterwhich has a hydrocarbon chain of eighteen carbon atoms, such asacetylated castor oil, butoxy ethyl stearate, or butyl acetylricinoleate. The heat stability of hydrogenated methyl abletate isgreatly improved by the addition of one or more of the aboveplasticizers, such as dioctyl phthalate, acetylated castor oil, butoxyethyl stearate and butyl acetyl ricinoleate. The combination of any orseveral of the above plasticizers with hydrogenated methyl abietate hasnot only good electrical properties but also good heat resistance. Byusing any of these plasticizing compositions in combination with vinylchloridevinyl acetate copclymer, an insulating and protective coveringfor wires may be obtained having a dielectric constant as low as 3 ,anda power factor as low as 3%.

The following method may be used to blend the plasticizar, and suchfillers as are used, with the resin. The resin is placed in a suitablecontainer and the plasticizer stirred into it. At this point a physicalmixture only is obtained since the resin, which will generally be two orthree times the volume of the plasticizer, will not dissolve in theplasticizer. Next, a preferably volatile solvent such as acetone isadded in suflicient quantity to form, on further stirring, a stifidough; and the mixture is stirred about five minutes to insure perfectdispersion of the acetone and plasticizer throughout the mass ofresinparticles, and then allowed to stand tightly covered for about tenminutes to give the acetone time to soften the individual resinparticles. Small tone-softened resin to combine with the plas ticizer.The heat causes the acetone to evaporate gradually, leaving the resinand plasticizer blended into a homogeneous mass. Finally, the

filler or fillers are added in the usual manner.

When the resin used in'such a composition is a copolymer of vinylchloride and vinyl acetate,

say in the ratio of from 85-95 parts of the chloride and 15-5 parts ofthe acetate, the proportion of the ingredients may be, for example, inaccordance with the following formula:

or again, in accordance with the following formula:

' Parts Resin (5% acetate) 100 Hydrogenated methyl abietate 40 Diootylphthalate 1o Butyl acetyl ricinoleate l Sublimed litharge 4 Blanc fixe20 The foregoing formulae, it will be understood,

are by way of example only. It will be noted that in the first of theseformulae the hydrogenated methyl abietate constitutes one-half of theplasticizing mixture and in the second, twothirds; these two formulaehave been selected to indicate, among other things, the approximateproportional range of the hydrogenated methyl abietate in theplasticizer which has been found to produce the best results. Both ofthe compounds produced thereby extrude easily, give smooth, shinysurfaces, are tough and flexible even at as low a temperature as -20 6.,and have good heat-aging properties at (7., and excellent electricalproperties. They are also re sistant to moisture, oil and flame. Theymay be applied bythe strip-covering method as well as by extrusion.Moreover, in addition to their use as insulation, they may be used asoverall jackets.

The drawing discloses in Figures 1 and. 2 an insulated conductorconstruction in which the conductor has applied thereto an insulatingcovering comprising vinyl chloride-vinyl acetate copolymer combined witha plasticizer as disclosed herein.

I claim as my invention:

A composition for use as an insulating and protective covering forconductors, comprising a copolymer of vinyl chloride and vinyl acetateas a base, and a plasticizer therefor comprising approximately equalparts of hydrogenated methyl abietate and a mixture containingacetylated castor oil, butoxy ethyl stearate, and butyl acetylricinoleate.

' ANSLEY 0. BLADES.

